Air deflector utilizing coanda effect



y 2, 1967 '0. HAYWOOD 3,316,657

AIR DEF'LECTOR UTILIZING COANDA EFFECT Filed Oct. 25, 1965 5Sheets-Sheet l y ?967 o. G. HAYWOOD 3,316,657

AIR DEFLECTOR UTILIZING COANDA EFFECT Filed Oct. 23, 1965 3 Sheets-Sheet2 P/Z/MAZ/ FZOIA/ F 1 7 IN VEN TOR. OZ/l/ /4 yh/oafl Arroen/af y 1967 0.5. HAYWOOD 3,316,657

AIR DEFLECTOR UTILIZING COANDA EFFECT Filed Oct. 23, 1965 3 Sheets-Sheet3 FIG; IQ

INVENTOR. 0L VER G. HA Yin 000 United States Patent 3,316,657 AIRDEFLECTOR UTILIZING COANDA EFFECT Oliver G. Haywood, New Canaan, Conn.,assignor to Huyck Corporation, Rensselaer, N.Y., a corporation of NewYork Filed Get. 23, 1965, Ser. No. 503,255 18 Claims. (Cl. 341l1) Thisinvention relates to the manufacture and processing of paper and, moreparticularly, is concerned with improved apparatus which is useful inthe dryer section of machinery on which continuous Webs of paper,meaning pulp, paper, paperboard, or other materials which are paperlikein form, may be made.

A typical continuous papermaking machine on which the invention taughtherein may be practiced is the socalled Fourdrinier machine, whichusually consists of three sections: the forming section, the presssection, and the dryer section. In the forming section, an aqueoussuspension of fibers is flowed onto an endless belt made from metal orsynthetic filaments, and most of the water is removed therefrom by theuse of well-known Water extraction devices, such as fols, table rolls,and suction boxes. The continuous web formed thereby is then transferredto and passed through a series of nips formed by press rolls, whichserves to remove additional water from the web and to compact it.Finally, the web is passed upward and downward over a series of heateddryer rolls or cylinders which are arranged parallel to each other intop and bottom arrays, for the purpose of further reducing its moisturecontent to the extent desired. In addition to efiecting drying by theapplication of heat to the web, such dryer rolls may be made with a gaspervious roll surface through which air or other suitable drying mediamay be forced.

As the formed web of paper comes into sequential contact with the heateddryer rolls, it is pressed against each such dryer roll by means of oneor more endless backing fabrics, which are usually referred to as dryerfabrics or dryer felts, in order to increase the heat transfer from therolls to the paper web, and to perfect the physical properties andcharacteristics of the finished sheet. Normally, separate dryer fabricsare used for the top and for the bottom dryer rolls. In the past, suchdryer fabrics have ordinarily been heavy, relatively impervious,blanketlike structures called dryer felts. More recently, dryer fabricsof a pervious or porous construction have been used whereby at leastsome of the moisture liberated from the paper sheet at it is pressedagainst each dryer roll can pass directly through such dryer fabric.Typically, such fabrics may be of Woven construction, but may also besheet-like belts which have been perforated, or other suitablestructures. Preferably, such fabrics, belts, or structures are made fromnatural and/or synthetic materials, such as polymer resins, which aremoisture resistant and substantially stable, physically and chemically,at the temperatures to which they are raised in the dryer section of thepaper machine. Such temperatures usually are at least 50 P. less thanthe maximum temperature of the dryer rolls which, in current practice,rarely exceed 425 F. Such fabrics, belts, or structures are madeendless, which is to say, into the form of a closed loop, by being wovenendless by the tubular weaving techniques which are well-known in theart of fabricating papermakers fabrics, or by being woven flat and laterhaving ends joined together by means of clipper hooks and pintle yarns,sewn seams, adhesives, ultrasonic sealing in the case of plasticsheet-like belts, or other Well-known joining techniques.

Regardless of which type of dryer fabric is employed, however, there isa tendency for the steam and/or moisture-laden air which is generated asa result of the drying 3,316,657 Patented May 2, 1967 'ice process tobecome entrapped on one or both sides of the dryer fabrics at variouspoints along their paths of travel. This is especially so wheretent-like pockets are formed by the various elements normally present inthe dryer section of the papermaking machine. One such group of pocketsis formed where atop dryer fabric is supported by rolls along its returnrun back toward the forward or Web receiving end of the dryer section.Another group of such pockets is formed directly below each of the topdryer rolls, and directly above each of the bottom dryer rolls; eachsuch pocket being an open-ended, substantially tubular enclosureextending in the cross-machine direction, directly below each such toproll or above each such bottom roll as the case may be, and beingbounded by the roll itself, the web of paper on each side of theenclosure, and the dryer fabric opposite the roll in question. Stillanother such group of pockets is formed where a bottom dryer fabric issupported by fabric rolls (sometimes referred to as pocket rolls)positioned between the bottom dryer rolls.

Such moist air and steam must, of course, be removed continually, inorder to ensure that the moisture content of the web may be controlledand to promote the efiiciency of the drying process. This is usuallyaccomplished by forcing air transversely through the dryer section usingsuitably positioned blowers, and by drawing air from the general area ofthe dryer section with overhead exhaust fans. However, the effectivenessof these removal procedures is not entirely satisfactory for a number ofreasons, among which are the resulting uneven temperature and moistureprofiles across the web. It is readily apparent, therefore, thatimprovement in such removal procedures is desirable and presentlyneeded.

It has now been found that the removal of such moist air and steam fromthe dryer section of a continuous paper-making machine utilizing one ormore pervious dryer fabrics can be materially facilitated. This objective is achieved in accordance with this invention by providing one ormore linear Coanda nozzles extending across the width of such dryerfabric at one or more desired locations adjacent to the broad surfacesof the fabric, and disposing such nozzles at an angle with respect tothe dryer fabric such that a transfer of gas, including steam and/ormoisture-laden air, from one side of the dryer fabric through the fabricto its other side will be effected.

The arrangement provided by the present invention maytake any of severalspecific forms of embodiment. For example, a linear Coanda nozzle my bepositioned closely adjacent to one side of the dryer fabric and disposedwith respect thereto at an angle diverging from the direction ofmovement of the dryer fabric, so that the nozzle will cause gas to besucked through the fabric from the opposite side of fabric to the nozzleside of the fabric. Alternatively, a linear Coanda nozzle may bepositioned on one side of the fabric and disposed with respect theretoat an angle converging toward the direction of movement of the dryerfabric, so that the nozzle will cause gas located on its side of thefabric to be propelled there through to the other side. In either case,the resulting effect of the action of the nozzle is to cause at least aportion of the gas on one side of the dryer fabric to flow through thefabric to the other side.

Advantageously, a converging nozzle positioned on one side of the dryerfabric as indicated above is utilized in conjunction with a divergingnozzle positioned on the other side of the dryer fabric, also asindicated above. The two nozzles in such case may be so situated withrespect to each other that the diverging nozzle acts in concert with theconverging nozzle, which is positioned on the opposite side of thefabric and tends to push gas through the fabric at the same time thediverging nozzle is sucking it through. It has been found that one wayto enhance such a concerted action of two nozzles is to position thediverging nozzle so that, using as a reference the direction of travelof the moving fabric, its point of divergence from the fabric isslightly ahead of the point of convergence of the other nozzle with thefabric, thereby causing gas pushed by the converging nozzle to flowthrough the fabric directly into the zone of suction created by thediverging nozzle on the opposite side of the fabric.

According to this invention, such a nozzle or set of nozzles, may belocated at any point or points along the path traversed by a dryerfabric where it is desired to effect a flow of gas, such asmoisture-laden air or steam, through the dryer fabric from one side tothe other thereof. For example, such a nozzle -or set of nozzles can beutilized in conjunction with a dryer fabric at any location along itsreturn run back to the forward end of the dryer section, to move gasupward through a top fabric (which backs the web against the topperiphery of each top dryer roll) or to move gas upward or downwardthrough a bottom fabric (which backs the web against the bottomperiphery of each bottom dryer roll). In addition, a plurality or seriesof two or more single nozzles or sets of nozzles may be used whereverappropriate.

Generally, nozzles may be formed from any suitable metal, although theymay also be made from a wide variety of other materials, such asplastic, wood, or Fiberglas.

It also will be apparent to those skilled in the art that while thedescriptions set forth herein are directed toward webs of paper, pulp,or paperboard, the principles of this invention may be practiced in awide variety of applications where it is desired to transfer a gaseousmedium from one side to the other of a moving pervious sheet, such as afabric, used in processing materials as, for example, in paper-coatingprocesses.

The invention will now be described in detail in connection with theaccompanying drawings, in which:

FIG. 1 depicts a straight jet emerging into a symmetrical boundary;

FIG. 2 depicts a straight jet emerging into a non-symmetrical boundary;

FIG. 3 depicts a jet deflected by the presence of a nonsymmetricalboundary, or so-called Coanda effect;

FIG. 4 depicts a jet turned through 180 using Coanda effect;

FIG. 5 is a cross-sectional representation of an ternal Coanda nozzle;

FIG. 6 is a cross-sectional representation of an external Coanda nozzle;

FIG. 7 is a cross-sectional representation of a composite Coanda nozzle;

FIG. 8 is a perspective view of a linear Coanda nozzle;

FIG. 9 is a diagramatic view of a portion of the dryer section of acontinuous papermaking machine provided with several installations of apreferred embodiment of this invention;

FIG. 10 is a diagramatic view of a portion of the return run of fabricin a dryer section of a papermaking machine which has been provided withan installation of another preferred embodiment of this invention; and

FIG. 11 is a diagramatic view of a portion of the return run of fabricin a dryer section of a papermaking machine which has been provided withan installation of still another preferred embodiment of this invention.

Before describing this invention, it will be necessary to explain thephenomenon known as Coanda Effect, which is most frequently described asa tendency for -a fluid to adhere to and be deflected by a boundary inits flow path. What is not so well-known is that the turning caused bythe presence of the boundary leads to a surprising degree of momentumand flow augmentation under certain conditions. It is these latteraspects of Coanda Effect which are particularly significant in theinvention described herein.

The phenomenon called Coanda Effect is easier to understand byconsidering first the two-dimensional case. Referring to FIG. 1, if aslot 1 exists between a chamber 2 of fluid at elevated pressure and aregion 3 of lower pressure, fluid will flow through the slot and emergein the form of a jet 4 into the region of lower pressure. This jet willhave a certain momentum, or product of mass'flow and velocity, whichwill be determined uniquely by the area of the slot and the pressuredrop across it. The flow of the jet will tend to produce a low-pressureregion 5 in the vicinity of the slot so that surrounding fluid isinduced to flow toward the jet and becomes entrapped by it. As mixingtakes place, the average velocity of the flow decreases and the massincreases until, at some distance away from the slot, the jet dissipatesin random motion of fluid particles. If one were to measure the totalmomentum of the flow at any point after emergence from the slot 1 itwould not exceed, at least in principle, the momentum at the slot 1, andas mixing increased, the random motion of particles would be expected todecrease with distance from the slot 1. All momentum changes would takeplace by collision of particles.

If the geometry in the vicinity of the slot opening is changed by theintroduction of a boundary 7 as in FIG- URE 2, it can be seen at oncethat the induced flow of fluid toward the jet 4 will be hampered on theside where the new boundary has been introduced. This will lead to aregion 8 of reduced pressure between the jet 4 and the boundary 7. Theexistence of the region of reduced pressure causes a deflection of thejet 4 which further reduces the pressure in the region 8 and leads tofurther deflection until, as shown in FIGURE 3, the jet lies on theboundary itself with a region 8 of greatly reduced pressure right at theboundary. By means of the same principle, the flow can be further turnedby successive changes in direction of the boundary as illustrated inFIG- URE 4, which may be made continuous so as to produce a smoothcurve.

The deflected jet now has three characteristics which are ofconsiderable interest. First, the velocity on the unbounded side of thejet will be equal to the velocity in the jet of FIGURE 1, while thevelocity everywhere else in the jet will be higher, due to the greaterpressure drop induced by the boundary 7. Hence, the average velocity ofthe deflected jet will be higher than the average velocity of a straightjet created by the same supply pressure chamber 2.

Second, since the pressure in the deflected jet is everywhere equal toor less than the pressure in the straight jet and the slot size remainsthe same, the average momentum of the deflected jet will be higher thanthat of a straight jet created by the same supply pressure.

Third, there will exist a pressure gradient across the jet which, understeady-state conditions, creates a static pressure field similar to thatcreated by flow past an airfoil. This field induces a secondary flow 13of considerable magnitude, and, depending on the geometry used, may beconverted into either high static lift or high mass-flow rates. Becauseof the momentum augmentation in the primary and because the secondaryflow 13 is induced by a pressure field rather than by less eflicientcollision processes, the total flow produced by the deflected jet ischaracterized by substantial momentum augmentation and a high degree ofenergy transfer efliciency.

The discussion so far applies generally to all fluids, whethercompressible or incompressible. If the fluid involved is compressible,there is an additional character istic of interest. With Coanda effect,the existence of an average pressure in the jet lower than ambient leadsto greater expansion of the fluid than would be the case with a straightjet, as evidenced by the momentum augmentation produced, so that lessrandom motion is evident in the combined exit flow from a Coanda nozzlethan would be expected from a conventional ejector. Since a greaterportion of the original potential energy in the primary emerges asordered kinetic energy, the exit temperature of the flow issubstantially lower than would be obtainable with a conventionalejector. This effect may prove to be of value in certain applications,such as the one herein described, where temperature rise must beminimized.

The foregoing discussion has considered Coanda Effect in only twodimensions. There are several ways in which the basic principle may beextended to three dimensions. First, we may create a figure ofrevolution about an axis internal and external nozzles to producecomposite nozzles Coanda Nozzle, shown in FIGURE 5. Also, rotation aboutan axis external to the flow produces an external Coanda Nozzle, as inFIGURE 6. Or we may combine internal and external nozzles to producecomposite nozzles of various types; for example, the type shown inFIGURE 7. Still another configuration, and the one which will beparticularly useful in the application herein described, is to use thetwo-dimensional configuration heretofor described in FIGURES 2 through 4and merely extend it flat through the third dimension, with thedeflecting boundary in the shape of a wing or a foil, as illustrated inFIGURE 8, thereby producing a linear Coanda nozzle. It will be notedthat this structure is, in effect, the internal Coanda nozzleillustrated in FIGURE 5 except in flat rather than circularconfiguration. The choice of embodiment depends upon the application andthe boundary conditions of the flow.

The dryer section partially shown in FIG. 9 includes a plurality ofhorizontally disposed top dryer rolls 10, 11, 12, and bottom dryer rolls31, 32, 33; all of which are rotatable and, usually, heated. Thecontinuously formed web 14 is successively passed between the top andbottom dryer rolls for the purpose of driving off residual moisture fromthe web to a predetermined extent. Means (not shown) are provided forrotating such dryer rolls in unison so that the continuous web 14 can bemoved through the dryer section without breaking. In addition, othermeans (not shown) are provided for controllably admitting steam or someother suitable heating medium into the dryer rolls in order to furnishthe heat utilized to effect the desired drying of the web. The surfacesof such rolls which come in contact with the web may optionally be solidor made from porous material such as sintered metal fibers, or sinteredpowder metal, or fused glass, or thermoplastic or thermoscttingmaterial, through which gas may be blown or sucked.

Movable in conjunction with the web and arranged to press such webagainst at least the top portion of each of the top dryer rolls 10, 11,12 is an endless, porous, top dryer fabric 16. As indicated in FIG. 9,such dryer fabric passes under rotatable fabric rolls 18, 19 positionedbetween each pair of dryer rolls somewhat below the center of rotationof each such dryer roll, so that good contact between the continuous web14 and the successive top dryer rolls is assured. On the return run(shown in the upper portion of FIG. 1), the dryer fabric 16 passes over(or under as required) a plurality of rotatable return rolls 20. Means(not shown) may be provided for rotating one or more of the fabric rollsand/or one or more of the return rolls as may be necessary to insureproper movement of the endless dryer fabric. Similarly, the bottom dryerrolls 31, 32, 33 are operated in conjunction with a bottom backingfabric 34, positioned below the bottom dryer rolls, which also issupported by fabric rolls 21, 23 positioned between the bottom dryerrolls, and by return rolls 20.

The result of the successive passage of the continuous web 14 around andin contact with the dryer rolls is the generation of steam throughliberation of moisture from the web. A portion of such generated steamescapes through the porous dryer fabric while the web 14 is held incontact with each dryer roll by the dryer fabric. The remainder of suchgenerated steam escapes as the continuous web is removed from intimatecontact with the surface portion of each dryer roll. In the former case,such steam tends to accumulate, for example, in the area under thereturn run portion of the endless dryer fabric 16, and in the pocketsformed by the bottom fabric 34 and the fabric rolls 21, 23; and in thelatter case pockets of steam tend to form, for example, in the pocketsformed above and below the dryer rolls by the dryer fabric, the web ofpaper, and the several dryer rolls. Of course, a certain amount ofmigration of such steam as well as heated, moisture-laden air upwardthrough the various layers of dryer fabric takes place by naturalconvection. However, in order to accelerate expulsion of such steam asit accumulates, means (not shown), such as fans, may be provided forcausing air to move transversely through the dryer section, and othermeans (not shown) may be provided for exhausting steam and/ ormoisture-laden air from the general region of the dryer section.

In accordance with the invention, such steam removal is aided by theprovision of one or more arrangements to facilitate the passage of moistair through a porous dryer fabric at points along its path of travelwhere it is not pressing the web into intimate contact with a dryerroll. Any number of such arrangement-s may be installed in a given dryersection as its layout permits, and such arrangements may take any ofseveral forms of embodiment, as previously indicated.

The five arrangements, 22, 24, 26, 35, and 38 shown in FIG. 9 aresimilar and comprise some of the preferred embodiments of the invention.As will be apparent, arrangement 22 is associated with the top dryerfabric 16 about midway between fabric roll 18 and dryer roll 11;arrangement 24 is similarly associated with the top dryer fabric 16about midway between fabric roll 19 and dryer roll 12; arrangement 26 isassociated with the top dryer fabric 16 along its return run portion;and arrangements 35 and 38 are associated with the bottom dryer fabric34 along its return run portion. Each such arrangement comprises alinear Coanda nozzle 28 positioned adjacent to one side of one of thedryer fabrics and extending in the cross-machine direction thereof, anda linear Coanda nozzle 30 located near the nozzle 28 and positionedclosely adjacent to the opposite side of the same dryer fabrictherefrom, and also extending in the cross-machine direction. Theprimary or inducing air flow in each such nozzle may be supplied bypneumatic feedlines (not shown), such as are commonly used around suchmachinery in connection with auxiliary mechanisms which, in turn, may besupplied by a compressor (not shown), or other air pressure source.

Each nozzle 28 is disposed with respect to the backing fabric at anangle converging in the direction of movement of such dryer fabric. Inother words, each nozzle 28 is so oriented in relation to the surface ofthe fabric that the flow of gas which it induces has its origin in theregion adjacent to the same surface of the fabric to which the nozzle 28is adjacent, and extends through the fabric into the region adjacent tothe opposite surface of the fabric.

Each nozzle 30 is disposed with respect to the backing fabric at anangle diverging in the direction of movement of such dryer fabric. Thatis to say, each nozzle 30 is so positioned and oriented with respect tothe surface of the dryer fabric that the flow of gas which it induceshas its origin substantially in the region adjacent to the surface ofthe fabric opposite the surface to which the nozzle 30 is adjacent, andextends through the fabric into the region adjacent to that surface ofthe fabric to which the nozzle 30 also is adjacent. Generally, such anozzle should be positioned so that it nearly touches the surface of thefabric in order to ensure that the preponderance or at least asubstantial portion of the induced air flow comes from the opposite sideof the fabric, but still far enough from the fabric to ensure that theprimary air flow from the Coanda nozzle is not interfered with.

The net effect of both the diverging nozzle and the converging nozzle 28is to set up a pressure gradient from one side of the dryer fabric tothe other side thereof, As a consequence, gas, such as moist air and/ orsteam, on one side of the dryer fabric is caused to fiow therethrough-It should be noted that in each of the embodiments illustrated in FIG.9, the converging nozzle 28 was positioned substantially opposite itsassociated diverging nozzle 30* but on the other side of the fabrictherefrom. By this means, gas may be moved from the zone of increasedpressure created by each converging nozzle 28 through the fabric anddirectly into the corresponding zone of de-- creased pressure createdbehind its associated diverging nozzle 30. In the case of arrangements22 and 24, moist air is moved from the steam pockets formed by the topdryer fabric 16 and the paper web with dryer rolls 31 and 32respectively into the region immediately above such top dryer fabric 16and the dryer rolls 11, 12, from whence it can more readily be blowntransversely out of the dryer section !by fans or other means ortransferred upward through the fabric 16 on its return run. Similarly,in the case of arrangement 26', the moist air is moved from the area ofaccumulation below the return run of the top dryer fabric 16 into theregion above such return run, from whence it can much more readily! beexhausted.

In arrangement 35, relatively cool and/or dry air is moved from belowthe return run of the bottom dryer fabric 34 through the fabric into thezone enveloped by the fabric 34. The effect of this is to replace thesteam; and moisture-laden air entrapped in that zone after liberationfrom the web 14 through the fabric 34 as they pass together over thesurfaces of the bottom, dryer rolls 31, 32, 33. Such replaced steam andmoisture-laden air will be forced outward from the zone of entrapmentboth ways in the cross-machine direction, and also will be forced upwardthrough the fabric 34 from the pockets formed by the fabric 34 as itpasses over the fabric rolls 21, 23 into the pockets formed by the topdryer rolls 11, 12 with the paper web and the bottom fabric 34, fromwhence it may be moved outward both ways from such pockets in thecrossqmachine direction by fans or other propelling means.

It will be noted that in all of the heretofore discussed arrangements22, 24, 26, 35, the natural tendency of the steam and/or moisture-ladenwarmed air to move upward through the layers of fabric has supplementedthe dynamic effect of each such arrangement. Arrangement 38 demonstrateshow the principles of this invention may be used advantageously tocounteract such a. natural tendency of relatively warm or hot gas torise through convection, in order to deal more effectively with theproblems heretofore discussed. In arrangement 38, in contrast toarrangements 22, 24, 26, 35, the converging nozzle 28 is positionedadjacent to the upper surface of the fabric 34; that is, the surfacetoward which air would naturally tend to move by convection. Divergingnozzle 30 is positioned adjacent to the lower surface of the fabric 34,substantially opposite the converging nozzle 28. The effect of thisarrangement is to overcome the natural tendency of hot air to moveupward through the fabric 34 by convection, to a point where steam orhot moisture-laden air, for example, in the enclosure formed by itsbacking fabric 34 actually will be moved downward through the fabric toits underside, from whence it may be exhausted away from the dryer areaby fans or other means.

It will be apparent that a similar arrangement might be used toadvantage at other points. Thus, by utilizing such an arrangement ofnozzles, for example, between bottom fabric roll 21 and the point ofcontact of the backing fabric 34 with bottom dryer roll 32, steam and/ormoistureladen air may readily be removed downward from the pocket formedby the bottom dryer fabric 34, the web 14, and the top dryer roll 11.Conversely, the nozzles could be arranged at this point to transfersteam and/or moisture-laden air upward from the pocket below the roll 21to the pocket above the roll 21. As will be clear, then, each of thearrangements heretofore described exerts a positive acceleration on thesteam or moisture-laden air being removed from the continuous web as itpasses through the dryer section, and facilitates removal of such airfrom the dryer section region.

The individual effect of such diverging and converging nozzles isillustrated respectively in FIGS. 10 and 11; each of which in itselfconstitutes another useful embodiment of this invention. Arrangement 41is shown in FIG. 10 as being associated with a top dryer fabric 16 alongits return run portion, although it could obviously be associated with abottom dryer fabric too. Arrangement 41 is comprised of the nozzle 42positioned on the top side of the dryer fabric and extending in thecross-machine direction thereof. Like nozzle 30 of arrangement 26 shownin FIG. 9, nozzle 42 is so disposed with respect to the dryer fabricthat an angle diverging therefrom in the direction of movement of suchdryer fabric. The effect is also similar in that gas, such as moist airor steam, on the under side of the backing fabric is induced to flowtherethrough to the side of the fabric adjacent to which the nozzle 42is positioned. Obviously such a diverging nozzle might be positioned onthe underside of a top or a bottom dryer fabric to cause gas to be movedthrough the fabric from the upper to the underside thereof in thefashion of nozzle 30 in arrangement 38 in FIG. 9.

Arrangement 50 is shown in FIG. 11 as being associated with a top dryerfabric 16 along its return run portion, although it too could beassociated with a bottom dryer fabric, as will be apparent from thediscussion which follows. Arrangement 50 comprises a nozzle 52positioned on the underside of the dryer fabric and extending in thecross-machine direction thereof. Like nozzle 28 of arrangement 26 shownin FIG. 9, nozzle 52 is also disposed with respect to the dryer fabricat an angle converging in the direction of movement of such dryerfabric. Again, a similar effect is obtained in that gas, such as moistair or steam, 0n the underside of the dryer fabric is also induced toflow therethrough to the side of the fabric opposite to that to whichthe nozzle 52 is adjacent. It will also be obvious that such aconverging nozzle might be positioned on the top side of a bottom or topdryer fabric to cause gas to be moved through the fabric from the upperto the underside thereof in the fashion of nozzle 28 of arrangement 38in FIG. 9.

It will be readily apparent that single vane embodiments, such as thosediscussed heretofore in connection with arrangements 41 and 50, are byno means confined, in their utilization, to any particular locationalong the path of travel of the dryer fabric with which they areassociated, but may be used to advantage at many different points alongsuch paths of travel, including locations between the dryer and fabricrolls. It will also be apparent that single vane embodiments may beadvantageously used in groups of several such single vanes each, withthe vanes in each group arrayed in proximity and sometimes tfevgn inparallel to each other along one surface of a given a ric.

It should be understood that the terms, and expressions used herein andthe embodiments which have been illustrated and discussed are by way ofillustration, but not of limitation, of the principles of thisinvention, and that this invention may be practiced in a Wide variety ofpapermaking and processing apparatus, as well as other machinery bypersons skilled in the art.

I claim:

1. In an apparatus for drying a continuous sheet of P p an endlesspervious belt movable in conjunction with said sheet and arranged topress said sheet against the drying means in said apparatus,

and a linear Coanda nozzle extending substantially in the direction ofthe width of said belt adjacent to one surface thereof at a desiredlocation along the path of travel of said belt where it is not incontact with said sheet,

said nozzle being so oriented with respect to said belt that the flow ofgas induced by said nozzle will originate in the mass of gas adjacent tothe same surface of said belt as is said nozzle, will converge with saidbelt at an acute angle to the direction of travel of said belt, and willpass substantially totally through said belt to the side of said beltopposite that to which said nozzle is adjacent.

2. The device described in claim 1 wherein said belt is made frommaterial which is characterized by resistance to moisture and by beingsubstantially physically and chemically stable at temperatures in therange to which said belt is exposed along its path of travel throughsaid apparatus.

3. The device described in claim 2 wherein said belt is made from asynthetic polymeric material.

4. The device described in claim 3 wherein said belt is a woven fabric.

5. The device described in claim 2 wherein said nozzle extends acrossthe full width of said belt.

6. In an apparatus for drying a continuous sheet of material,

an endless pervious belt movable in conjunction with said sheet andarranged to press said sheet against the drying means in said apparatus,

and a linear Coanda nozzle extending substantially in the direction ofthe width of said belt adjacent to one surface thereof at a desiredlocation along the path of travel of said belt Where it is not incontact with said sheet,

said nozzle being so oriented with respect to said belt and sopositioned with respect to said surface of said belt that at least asubstantial portion of the flow of gas which is induced by said nozzlewill originate in the mass of gas adjacent to the surface of the beltopposite that to which said nozzle is adjacent, will pass through saidbelt, and will diverge from the surface of said belt at an acute angleto the direction of travel of said belt into the mass of gas adjacent tothe same surface of said belt as said nozzle.

7. The device described in claim 6 wherein said belt is made frommaterial which is characterized by resistance to moisture and by beingsubstantially physically and chemically stable at temperatures in therange to which said belt is exposed along its path of travel throughsaid apparatus.

8. The device described in claim 7 wherein said belt is made from asynthetic polymeric material.

9. The device described in claim 8 wherein said belt is a woven fabric.

10. The device described in claim 7 wherein said nozzle extends acrossthe full width of said belt.

11. In an apparatus for drying a continuous sheet of material,

an endless pervious belt movable in conjunction with said sheet andarranged to press said sheet against the drying means in said apparatus,

and a first linear Coanda nozzle and a second linear Coanda nozzle, bothof which extend substantially in the width direction of said belt onopposite sides thereof from each other at desired locations along thepath of travel of said belt where it is not in contact with said sheet,

said first nozzle being so oriented with respect to said belt that theflow of gas induced by said first nozzle will originate in the mass ofgas adjacent to the same surface of said belt as is said first nozzle,will converge with said belt at an acute angle to the direction oftravel of said belt, and will pass substantially totally through saidbelt into the mass of gas adjacent to the side of said belt, oppositethat to which said first nozzle is adjacent, said second nozzle being sooriented with respect to said belt and so positioned with respect to thesurface of said belt that at least a substantial portion of the flow ofgas induced by said second nozzle will originate in the mass of gasadjacent to the surface of the belt opposite that to which said nozzleis adjacent, will pass through said belt, and will diverge from thesurface of said belt at an acute angle to the direction of travel ofsaid belt into the mass of gas adjacent to the same surface of said beltas is said second nozzle.

12. The device described in claim 11 wherein said belt is made frommaterial which is characterized by resistance to moisture and by beingsubstantially physically and chemically stable at temperatures in therange to which said belt is exposed along its path of travel throughsaid apparatus.

13. The device described in claim 12 wherein said belt is made fromsynthetic polymeric material.

14. The device described in claim 12 wherein substantially all of theflow of gas induced by said first nozzle will flow directly into theflow of gas induced by said second nozzle.

15. The device described in claim 13 wherein said belt is a wovenfabric.

16. The device described in claim 14 wherein said belt is a wovenfabric.

17. The device described in claim 15 wherein said nozzle extends acrossthe full Width of said belt.

18. The device described in claim 16 wherein said nozzle extends acrossthe full width of said belt.

References Cited by the Examiner UNITED STATES PATENTS 2,052,869 4/1936Coanda 2392 2,082,411 6/1937 Merrill 34160 X 2,574,844 11/1951 Roden34-l60 X FREDERICK L. MATTESON, 111., Primary Examiner. A. D. HERRMANN,Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE- OF CORRECTION Patent No 03,316,657 May 2 1967 Oliver Ga Haywood error appears in the abovenumbered pat- It is hereby certified that t the said Letters Patentshould read as ent requiring correction and the corrected below.

Column 1, line 23, for "015" read foils line 49, for "at" read as column5, line 4, for "obtainable" read obtained line 12, for "and externalnozzles to read to the flow and produce a produce composite nozzlesso-called "internal" Signed and sealed this 28th day of November 1967c(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

1. IN AN APPARATUS FOR DRYING A CONTINUOUS SHEET OF PAPER, AN ENDLESSPERVIOUS BELT MOVABLE IN CONJUNCTION WITH SAID SHEET AND ARRANGED TOPRESS SAID SHEET AGAINST THE DRYING MEANS IN SAID APPARATUS, AND ALINEAR COANDA NOZZLE EXTENDING SUBSTANTIALLY IN THE DIRECTION OF THEWIDTH OF SAID BELT ADJACENT TO ONE SURFACE THEREOF AT A DESIRED LOCATIONALONG THE PATH OF TRAVEL OF SAID BELT WHERE IT IS NOT IN CONTACT WITHSAID SHEET. SAID NOZZLE BEING SO ORIENTED WITH RESPECT TO S AID BELTTHAT THE FLOW OF GAS INDUCED BY SAID NOZZLE WILL ORIGINATE IN THE MASSOF GAS ADJACENT TO THE SAME SURFACE OF SAID BELT AS IS SAID NOZZLE, WILLCONVERGE WITH SAID BELT AT AN ACUTE ANGLE TO THE DIRECTION OF TRAVEL OFSAID BELT, AND WILL PASS SUBSTANTIALLY TOTALLY THROUGH SAID BELT TO THESIDE OF SAID BELT OPPOSITE THAT TO WHICH SAID NOZZLE IS ADJACENT.